1. Field of the Invention
The present invention relates to thermography, namely, the printing of visual matter by means of heat, and, more particularly, to the formation of visual matter in terms of visual dots transferred to a paper or textile web from a pigment or dye carrier under the control of an array of thermal elements.
2. The Prior Art
A variety of systems have been proposed in which individual thermal elements produce indicia or patterns on a web in response to readout commands. In one such system, typified by U.S. Pat. No. 3,815,144, June 4, 1974, in the name of Howard H. Aiken for Thermal Recorder Having An Analogue To Digital Converter, an array of thermal elements produce visual matter directly on thermally sensitive paper. In another such system, typified by U.S. Pat. No. 3,596,055, July 27, 1971, in the name of William A. Elston for Method And Apparatus For Producing Displays Utilizing An Electronic Display System, an array of thermal elements produce visual matter by transfer of a visual medium from a carrier to ordinary paper or the like. Such thermal systems contrast with mechanical impact systems, which tend to be less adapted to meet special readout requirements, particularly, very high speed and unusual versality. In connection with such thermal systems, it is desired to increase speed and improve versatility without adversely affecting reliability or unduly increasing cost.